It is the objective of this project to develop microwave exposure systems for bioeffects research and to develop and test techniques for measuring energy absorption. The waveguide system for exposing isolated neurons to 2450 MHz microwave radiation has been modified so that longer survival times and constant temperatures of the nerves during exposure could be achieved. Small thermistor probes have been used to measure deep colonic temperatures in pregnant mice during exposures to 2450 MHz microwave radiation. Using the temperature profiles measured in the dead animals to calculate average absorption rates, the results agreed well with both calculated and measured whole body absorption reported in the literature. A system for exposing groups of marine animals to different intensity levels simultaneously without significant perturbation of the microwave field by the location and orientation of the animals has been developed and tested. A system to expose localized areas or organs in animals has been assembled for use in physiological studies.